Effects of Microplastics on Fishes

The effects of MP contamination on fish health are not yet fully understood. The ingestion of MPs by fishes can get accumulated in their digestive tract, which can cause starvation

TABLE 12.2 Summary of MP Effects

Effect

Description

References

Increased reactive oxygen species (ROS)

Ingested microplastics have shown to increase free radicals, which leads to cellular and DNA damage.

[44]

Reduced feeding or filtering

Animals containing microplastics in their digestive tracts were found to eat less, resulting in lower energy levels and fat reserves.

[42,43]

Immune response

Microplastics in animal tissue can induce an immune response leading to inflammation.

[45,46]

Hepatic damage

Owing to metabolic stress caused by microplastics, as well as pollutants accumulating on the surface, liver damage has been found in some organisms.

[47,48|

Reduced gamete quality

Lower gamete quality causes fewer offspring to be produced and decreased fecundity.

[49]

Mortality

Owing to a combination of the physical and physiological effects of microplastic particles on certain individuals, fatality' is increased.

[23]

Source: Bouwman H et al. Microplastics in Freshwater Environments, 1 edn., Water Research Commission, Republic of South Africa, 2018, pp. 5-22.

because of the false sensation of satiation or even perforation of the gastrointestinal tract. It may also pass to predators including humans [38-40]. Internal and digestive enzyme systems may get damaged; even reproduction can be affected because of MPs digestion [41-43]. Examples of studies are listed in Table 12.2.

As MPs act as a sponge and provide surface area for various bio-organic or inorganic toxic substances; the ingestion of these adsorbed toxin-containing MPs could be a serious health issue for the fishes. The negative effect of toxins on fish health was demonstrated by [47,48]. Tiny particles of low-density polyethylene (LDPE) were exposed to environmental bay conditions for 3 consecutive months and then fed to fishes. After 2 months, the tissues of fish had a greater concentration of PBTs and showed signs of liver stress, glycogen depletion, fatty vacuolation and cell necrosis [47,48] (Figure 12.5).

A total of 21 studies reporting ecotoxicological effects of MPs were identified. Fishes may ingest MPs either directly or by the prey containing these particles [51]. Overall documented effects of MPs on fishes include reduction of feeding activity [52,53], oxidative stress [54], genotoxicity [54], neurotoxicity [55-58], growth delay [54,59,60], reduction in reproductive fitness [23,61] and ultimately death [23,59,61,62]. The representation of ecotoxicological effects is shown in Figure 12.6.

 
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